Question

Discuss the role of Lewis acids in the preparation of aryl bromides and chlorides in the dark.

Answer 1

Lewis’s acids are electron-deficient species. They are responsible for inducing heterolytic fission in halogen molecules. The role of Lewis acid is to produce an electrophile, The electrophile produce will attack electron-rich benzene ring to produce aryl bromides and chlorides

$\text{Preparation of aryl bromide}$

$AlB{r}_3+B{r}_2⟶[AlB{r}_4{]}^{-}+B{r}^{+}$

$AlB{r}_3+B{r}_2⟶[AlB{r}_4{]}^{-}B{r}^{+}$



$\text{Preparation of aryl chloride}$

$AlC{l}_3+C{l}_2⟶[AlC{l}_4{]}^{-}+C{l}^{+}$

This electrophile will attack benzene ring